Chemical immersion heater



Nov. 6, 1945. w. A. CALDWELL CHEMICAL IMMERSION HEATER Filed Jan. 9, 1942 Patented Nov. F. 1945 UNITED STATES PATENT oEFlcE CHEMICAL IIHMERSION HEATER .Walter Anderson Caldwell, Seamill, Scotland, as-

signor to Imperial Chemical Industries Limited, a corporation of Great Britain Application January 9, 1942, lSerial No. 426,234 In Great Britain October 25, 1940 8 Claims. (Cl. 126-263) This invention relates toa heating device, and device. Also according to the invention the heatin particular' to an immersion heater suitable for er may be internally lined with heat insulating use. when ordinary heating appliances are not material, e. g. with asbestos paper, at the portion available or are inapplicable, the heating material containing the charge, the purpose of the lining employed being such as to give rise to no inilambeing to prevent heat flowing to the exterior of mable vapours on storage. the tube too fast and so causing singeing, char- Circumstances often arise when it isdesirable ring or other local overheating effects. Alterto have the means for heating materials such as nately the tube may be made of poorly conductwater or liquid foods when there is no access to ing material. gas or electric supply or ordinary kitchen heating 10 According to a further feature of the invention apparatus. Numerous forms of portable stoves the tube may be made so that after the reaction burning volatile fuels are known, but the immeris over the residue can be removed and replaced sion heaters of the present invention can be emwith a new charge, and, if necessary, a new igniployed in situations in which volatile fuels are tion device; while a further feature of the inveninapplicable or cannot conveniently be used, for tion comprises a reloadable tube which is adapted instance under rough Weather conditions or in to accommodate charges of different sizes, so that confined spaces such as rooms sealed against the the user can adjust the charge to the quantity f entry of poison gas. They are more easily hanof substance he wishes to heat.

dled than stoves. The heating mixture may comprise a pulver- It has been proposedtouse for heating purposes ulent metal alloy or silicideand a pulverulent chemical compositions which generate heat when oxidising agent that react together when thermoistened, but the compositions employed have mally initiated to yield intense heat but little only a low heat evolution and have not been used or no gas. Suitable mixtures may be formed for in immersion heaters. instance from calcium silicide and red lead and/or According to the invention an' immersion heatz5 iron oxide (hammerslag), aluminium and ironer comprises a container charged with a comoxide, ferrosilicon and red lead, or antimony and `position. comprising ingredients capable, on ignipotassium permanganate. Other combinations of tion, of undergoing chemical reaction with the oxidising and reducing agents on which the heatgeneration of heat but substantially without the ing mixture may be based include mixtures of evolution of iniiammable gas' or vapour; means 30 antimony, zinc and potassium permanganate;

operable from outside the container for igniting antimony alloys and oxidising agents such as pothe said composition; a vent leading from the tassium permanganate; red lead and sulphur; space occupied by the said composition to the mixtures' of selenium or tellurium with oxidising exterior of the immersion heater; ltering means agents such as barium peroxide or potassium perinterposed between the heating composition and manganate; red lead and ferrosilicon 87:13, lead the exit from the vent adapted to permit the paschromate calcium .silicide 90:10, zinc potassium sage of any heated air or gas but to retain any permanganate 60:40, iron potassium permangasolid particles; and heat insulation interposed benate 30:70, tin lead peroxide 35:65, tin potastween the heating charge and the surface or sursium permanganate 40:60, magnesium barium faces of the container adapted to come into con- 40 peroxide 6:94, calcium silicide red lead 30:70.

tact with the immersion medium when the heat- The intensity of the reduction may be coner is in normal use; the immersion heater being trolled b y varying the proportion of reducing also so adapted that in such use the exit, from the agent to oxidising agent, or by the inclusion of vent is outside the said immersion medium. The such ingredients as talc or china clay, or other heating charge suitably comprises a mixture of chemically inert heat absorbing solid diluent, but solid oxidising and reducing agents adapted to the mixture should be such as to assume a red react with the generation of intense heat and subto white heat when ignited in an uncooled vessel. stantially without the evolution of gas. The con- The mixture may be compressed or caked to minitainer may advantageously be tubular and the mise its bulk. invention will be described hereinafter with ref- The ignition means operable from the exterior erence to a tubular container. may comprise an element adapted to be initiated It must either be provided with a device whereby a small source of heat such as a match fuzee by it can be held with the opening of the tube or the like, for instance a length of touch paper outside the substance being heated, or also be of coated with a nitrocellulose composition and dustsuch shape that an end can itself act as such a ed with a slag forming igniting mixture, or a length of quickmatch fuze or some other type of fuze passing through the vent. The fuze composition may itself be of a gasless nature. Percussion or friction ignition means may however be provided.

Since the heating mixture may be difficult to ignite it is in some cases desirable, especially when the mixture has been diluted with inert heat absorbing material, to provide an intermediate priming charge, which may advantageously consist of an easily ignitable gasless mixture.

The tube can be made of any substance which will withstand having simultaneously one side submitted to the high temperature of combustion and the other side to the cooling effect of being in contact with the substance being heated. For instance a tube of thin sheet steel, tin plate, brass or silicate may be used. It may be made for instance from sheet metal by any method yielding a gas tight closure, such as drawing orfolding, seaming and soldering.

The end and a portion of the side may be lined with a layer of asbestos, china lclay, sodium silicate mixture, or other heat resisting material.

As ignition means a fuse may be introduced through the venting means into the tube so that one end is embedded in the heating mixture,

The filtering means may advantageously consist of a plug of glass wool or asbestos wool and the fuse may pass through it.- According to one form of the invention the part of the tube which remains empty may be pressed fiat. This prevents the contents of the tube from falling out, grips the fuse in position, while the presence of the fuse prevents the tube from being entirely flattened and ensures a passage' for the egress of the heated air.

'For storage and transport the event and the ignition means may be temporarily closed in, for instance by means of adhesive tape or paper, a vsoldered metal tear off or the like.

In use the end of the heater containing the charge is placed in contact within the substance to .be heated in such a way that the whole of this part of the heater is embedded or immersed in the substance, while the vent is kept outside. The fuse is then ignited and in its turn ignites the heating mixture which rapidly reacts leaving a residue at a very high temperature.

Another form of immersion heater which can be reloaded comprises a tube having at the base a layer of heat insulating material. Into the bottom of this tube are dropped one or more pellets of the heating mixture, possibly containing a small quantity of silicate, to act as a binder.

' Each pellet is made up with a tubular layer of heat insulating material surrounding it4 and of such size as to fit conveniently into the heater. Above the pellets of heating mixture is placed a perforated metallic, disc'having an ignition composition on the side facing the heating material and having a tubular extension parallel to the tube in the opposite direction, which extension is crimped around the end of a piece of safety fuse. 'I'his tubular extension is adapted to pass into a central tube which passes right through a removable block of glass wool or other filtering material, which is held in shape by a perforated plate at each end. A perforated cap can be screwed into the open end of the tube carrying a spring which presses on the filter and so keeps the contents of the tube in position. A length of the safety fuse will pass through this cap.

This invention is as illustrated by the accompanying drawing in which Figures 1 and 2 are two cross sections at right angles to each other through the axis of the heater. Figure 3 illustrates the heater in use to boil a kettle of water, while Figure 4 illustrates a section through a form of heater which can be reloaded. Referring to Figures 1 and Z, the outer case I of thin steel is cylindrical at one end and flattened at the other. The cylindrical end is closed. A lining 2 made by a mixture of china clay and sodium silicate is placed in the cylindrical portion of the-I heater forming a cup shaped receptacle which is filled with the heater composition 3 consisting of 35 parts of calcium silicide, 65 parts ofy red lead and 8 parts of talc. Above this heating mixture is a block 4 of glass wool. Through this block of glass wool is the fuse 5 which extends from the open end of the heater to a priming composition 6 consisting of a mixture of calcium siliclde and red lead. The top end of the tube is closed by a protective layer 'I of adhesive tape.

The method of using the heater is illustrated in Figure 3. The heater is dropped into a kettle with theflattened end sticking out through the lid opening.

'I'he lid is placed so that it closes as much of the opening as possible so as to preserve the heat. The protective tape 1 is then torn off and the match applied to the end of the fuse. We have found that by using a heater containing gm. of the above heating mixture that we can bring to the boil 1 pint of water in 90 seconds. Instead of putting the lid into place as shown in Figure 3 it is sometimes an advantage to stir the liquid which is being heated with the immersion heater.

Referring to Figure 4 a metal container 20 having tubular side walls I5 is fitted with a screw cap 22 which is perforated centrally at 23 to take the end of the safety fuse and also at 24 to allow the escape of gases from inside the tube. At the foot of the tube I5 is a lining 25 of china clay and sodium silicate. Two charges 26 each having i previously been made up with a tubular layer 21 of china clay and sodium silicate are placed on top of the heat insulating layer 25. On the top of the upper pellet of heating material is pressed a layer 8 of ignition composition, which layer is carried .by perforated plate 9 having a tubular extension I0 crimped on to av safety fuse I I which passes through the central hole 23 of the cap 22. The tubular extension I0 and the safety fuse II pass into a metal tube I2 which extends between two perforated plates I3 and I4 which together with the tubular member I5 enclose the filter of glass wool I6. This filter is pressed in a downward direction by the spring I1 which abuts on the cap 22.

To reload the device after it has been used the cap 22 is removed and the filter is pulled right out of the tube by means of the remains of the safety fuse II which together with the plate 9 is then discarded. The slag of the heating mixture will still be enclosed in the china clay and silicate tubes and can be jerked out of the tube.

In accordance with the amount of liquid which is to be heated a number of pellets are introduced into the tube. The user is provided with an ignition mixture fitted to a new plate 9 with the new safety fuse I I, crimped into the extension III. The fuse is first threaded through the tube 4I,2 and then the fuse and filter are together pressed into the tube, the spring I1 placed on top and the cap 22 screwed into place.

I claim:

l. A portable immersion heater comprising an elongated container having a closed end, a 1inascenso chemically and produce heat upon ignition, a.

filter substantially coextensive in cross-sectional area with the interior of the container above the charge, comprising a gas pervious plug of substantial thickness of refractory wool through which gases from the charge may pass and having a central fuse passage therethrough,

means for coniining the lter and the charge in the container, vent means in the other end of the container through which gases passing through the body oi the plug may escape to the outside, and a fuse accessible from the outside and extending through the vent means and the central passage in the lter to said charge.

2. A portable immersion heater comprising an elongated tubular container having a body closed at one end and lined with heat-insulating material, means dening a vent opening of restricted size, an elongated hollow neck of corresponding size projecting from the vent opening and providing an elongated vent passage, a charge of ignitable heating composition confined in the body adjacent the closed end thereof, said charge having ingredients which neact chemically and produce heat upon ignition, and a fuse accessible from the outside and extending through the vent passage and vent opening to the charge.

3. A portable immersion heater adapted for insertion in a vessel toheat the contents thereof, comprising a tubular container having a body closed at one end and lined with heat-insulating material, means at the other end of the body defining a vent opening of restricted size, an elongated hollow neck projected outwardly from the vent opening and providing e. vent passage of correspondingly restricted size adapted to discharge exteriorally of the vessel to be heated. a charge of heatixrg composition conned in the body adjacent the closed end thereof, said charge having ingredients which react chemically and produce heat upon ignition, a lterof porous refractory material of substantial thickness in the body between the charge and the vent opening and substantially coextensive in cross-sectional area with the interior of the body, and a fuse accessible from the outside and extending through the vent passage, the vent opening and the filter to the charge.

4. A portable immersion heater adapted for insertion in a vessel to heat the contents thereof,

comprising a tubular container having a body closed at one end and lined with heat-insulating material and having an integral elongated neck of restricted cross sectional area. extending outwardly from the outer end thereof and providing an elongated vent passage` adapted to discharge exteriorly of the vessel to be heated, a charge of sage and of substantially the same cross-sectional area as the charge. and a fuse extending from the outer end of the passage through the filter to the charge.

5. A portable immersion heater adapted for insertion in a vessel to heat the contents thereof comprising a tubular container closed at one end and lined with heat-insulating material and having a attened neck oi restricted cross sectional area extending outwardly from the other end thereof and providing a vent passage adapted to discharge exteriorly of the vessel to be heated, a charge oi heating composition in the body adjacent the closed end thereof, said charge having ingredients which react chemically and produce heat upon ignition, a lter interposed between the charge and the vent passage, and a fuse ex tending from the outer end of the passage through the iilter to the charge.

6. A portable immersion heater adapted for insertion in a vessel to heat the contents thereof, comprising a tubular container closed at one end and internally lined with heat-insulating material adjacent its closed end, a substantial portion of the body of said .container extending to its opposite end being attened to provide a Vvent of restricted cross sectional area., adapted to discharge exteriorly of the vessel to be heated, a charge of heating composition conned in the closed end of the container, said charge having ingredients which react chemically and produce heat upon ignition, a filtering substance of substantial thickness packed upon the charge of heating composition between the charge and the flattened end of the body and coextensive in cross-sectional area. with the charge, and a fuse communicating with said charge and extending through the ltering substance and the vent for access from the exterior of the heater.

'1. A portable immersion heater comprising a tubular container having a closed end lined with heat-insulating material, a. charge of heating .composition in the container surrounded by said lining, said charge having ingredients which react chemically and produce heat upon ignition, a plug of refractory ltering material having a central bore disposed in the container above the charge, a priming device between the filter and the charge, means for retaining the filter and the priming device in the container, and a. fuse extending from the outside through the last-mentioned means and the filter to the priming device.

8. A portable immersion heater comprising a tubular .container having a, closed end lined with heat-insulating material, a. charge of heating composition in the container surrounded by said lining, said charge having ingredients which react chemically and produce heat upon ignition. a. primer adjacent the heating charge, a plug of refractory filtering material between the charge and the other end of the container, an apertured closure for the latter end of the container,l a. spring between the closure and the plug for holding-the plug and the-charge in the container, and a fuse extending from the outside through the closure. the spring and the plug to the primer.

WALTER ANDERSON CALDWELL.. 

